The invention relates to a system and method for safe high-temperature operation of a flash memory as may find application, more particularly, in conjunction with automotive transmission controllers.
Employing flash memories (e.g. FEPROMs) in motor vehicles for memorizing vehicular parameters offers the possibility of cost-effective large-scale production of, for example, a transmission controller which is not programmed until being installed in a vehicle type. Flash memories feature a high storage density and permit blockwise clearing, whereby a speedy and simple programming is ensured. However, making use of such memories at high temperatures exceeding 100xc2x0 C. as may be encountered in the field of automotive engineering, e.g. in the region of the transmission in the environment of which the flash memory may be located, poses serious problems becausexe2x80x94due to electron mobility which increases exponentially with temperaturexe2x80x94the storage locations lose their charge with time, resulting in the data retention time being reduced.
It is thus the object of the invention to provide a system and method for operating a flash memory, in which the risk of data being lost due to use at high temperaturesxe2x80x94as may be encountered e.g. in the region of a transmission of a motor vehicle, is reduced.
This is achieved in a system for safe high-temperature operation of a flash memory which is programmed prior to use at high temperatures such that each data set in the flash memory is saved redundant. The system comprises:
a temperature sensor delivering temperature signals and sensing a temperature characterizing a temperature of the flash memory, and
a control unit connected to the temperature sensor and the flash memory, the control unit comprising a timer and being configured such that it receives the temperature signals from the temperature sensor and is able to establish an accumulated heat load value of the flash memory by integrating the determined temperature values versus time and then
when the accumulated heat load value exceeds a predefined heat load limit and
the temperature characterizing an actual temperature of the flash memory drops below a predefined temperature limit selected such that a safe clearing/programming of the flash memory is possible,
checks the sets of data for consistency, the control unit then
when it has established consistency of a data set, being able to carry out a refresh of storage locations of the flash memory which are associated with the data set and then
when it has established that one of the redundantly memorized sets of data is not consistent with one or more corresponding sets of data matching therewith, is able to repair the flash memory on the basis of a correct data set by reprogramming the incorrect data set such that it is consistent with the correct data set.
When an error occurs in a data set the control unit is firstly able to change over to another data set, due to the redundancy of the memorized data, and secondly to repair the faulty set of data on the basis of the other data set. Furthermore, regularly refreshing the memory content reduces the risk of loss of data due to high temperatures.
The object of the invention is further achieved by a method for safe high-temperature operation of a flash memory comprising at least one data set and being programmed prior to use at high temperatures such that each of said sets of data in said flash memory is saved redundant, said method comprising the following steps:
sensing a temperature characterizing a temperature of said flash memory, and
integrating said sensed temperature values versus time to establish an accumulated heat load value of said flash memory and
checking said sets of data for consistency,
when said accumulated heat load value exceeds a predefined heat load limit and
when said temperature characterizing an actual temperature of said flash memory drops below a predefined temperature limit selected such that a safe clearing/programming of said flash memory is possible, and
when consistency of one data set is established, there is carried out a refresh of storage locations of said flash memory which are associated with said data set, and
when it is established that one of said redundant memorized sets of data is not consistent with one or more corresponding sets of data matching therewith, said incorrect data set in said flash memory is repaired by reprogramming on the basis of a correct data set such that it is consistent with said correct data set.
Further aspects and advantages of the invention read from the sub-claims.